1. Field of the Invention
The present invention relates to orthopaedic reamers, and, more particularly, to reduced profile orthopaedic reamers.
2. Description of the Related Art
Minimally invasive surgery includes procedures that accomplish the elements of surgery (diagnosis, staging, resection, and repair, for example) with a minimal amount of psychological and somatic trauma. The technological procedures available for use by surgeons include methods for operating on patients with ever-smaller incisions, less operative risk, and quicker recoveries.
In total-hip replacement surgery, for example, the hip socket or acetabulum and the femoral head are typically badly deteriorated due to arthritis, or some other condition. In elderly patients particularly, this diseased condition dictates the removal of the head (ball) of the femur and its replacement by a polished metal (or other suitable material) ball with a shaft anchored in the intramedullary canal of the femur. To provide a proper bearing surface for the ball, one that will not limit the normal motion of the leg, it is necessary to reform the normal socket, or acetabulum, reaming away the diseased bone and cartilage to make a new structural base to receive a metallic or plastic (or other suitable material) socket matched to the artificial femoral head. The artificial socket is affixed within the reformed acetabulum by way of a suitable cement.
In shaping the acetabulum to receive the artificial socket, the acetabulum is undercut with an orthopaedic reamer so as to provide a surface against which the cement and artificial socket are seated and thus anchored to the bony structure of the acetabulum. Acetabular reamers are surgical tools, which are used to cut hemispherical cavities in the acetabulum for the insertion of artificial hip joint socket as described above. An acetabular reamer is typically composed of an acetabular reamer cup mounted on a tool driver, which in turn is mounted in the chuck or collet of a portable drill or flexible powered shaft. Acetabular reamer cups have an arrangement of precisely shaped cutting surfaces extending outwardly from an essentially hemispherical shell. Acetabular reamer cups are separable from their tool drivers for changing cup size prior to or during surgery, cleaning, and/or sharpening.
Acetabular reamers must be capable of producing cavities with very close tolerances. Acetabular reamer cups have precise dimensions and are light in weight and must fit on an appropriate tool driver with a minimum of free play and must be quick and easy to install and remove preferably without tools.
Because of the differing sizes, ages and physiologies among hip replacement patients, reamers of differing sizes are required. Hemispherical reamers are known which have diameters in the approximate range of 1.0 inches to 2.5 inches and which require a corresponding incision. If the reamer profile, which is introduced to the incision, can be reduced then the incision can be reduced thereby facilitating a more minimally invasive surgery.
Reamers are known which have portions of the hemisphere removed to reduce the profile presented to the incision and which thereby fit into the incision with less damage to soft tissue. However, these reamers have undesirable cutting performance such as eccentric cutting, uneven action and edges that catch on protruding anatomy. This undesirable cutting performance is due to the resulting reamer geometry after the portions are removed, which creates a rotationally unbalanced and unstabilized reamer geometry.
What is needed in the art is an orthopaedic reamer, for minimally invasive surgery, with a reduced profile and which has minimal or no degradation in cutting performance.